21.It is known to all that gunpowder is ___ Chinese invention,as is the compass,___ instrument that you use for finding directions.A.a; the.B/; an C.a;an D./;the

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21.It is known to all that gunpowder is ___ Chinese invention,as is the compass,___ instrument that you use for finding directions.A.a; the.B/; an C.a;an D./;the

C.a;an
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21. ....................................................................................an